Subject: Re: [PATCH V7 04/17] PCI: Take additional IOV BAR alignment in sizing and assigning

From: Wei Yang <[email-masked]>
Date: Wed, 20 Aug 2014 14:14:02 +0800

On Tue, Aug 19, 2014 at 09:08:41PM -0600, Bjorn Helgaas wrote:
>On Thu, Jul 24, 2014 at 02:22:14PM +0800, Wei Yang wrote:
>> At resource sizing/assigning stage, resources are divided into two lists,
>> requested list and additional list, while the alignement of the additional
>> IOV BAR is not taken into the sizeing and assigning procedure.
>> 
>> This is reasonable in the original implementation, since IOV BAR's alignment is
>> mostly the size of a PF BAR alignemt. This means the alignment is already taken
>> into consideration. While this rule may be violated on some platform.
>> 
>> This patch take the additional IOV BAR alignment in sizing and assigning stage
>> explicitly.
>> 
>> Signed-off-by: Wei Yang <[email-masked]>
>> ---
>>  drivers/pci/setup-bus.c |   68 +++++++++++++++++++++++++++++++++++++++++------
>>  1 file changed, 60 insertions(+), 8 deletions(-)
>> 
>> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
>> index a5a63ec..d83681f 100644
>> --- a/drivers/pci/setup-bus.c
>> +++ b/drivers/pci/setup-bus.c
>> @@ -120,6 +120,28 @@ static resource_size_t get_res_add_size(struct list_head *head,
>>  	return 0;
>>  }
>>  
>> +static resource_size_t get_res_add_align(struct list_head *head,
>> +		struct resource *res)
>> +{
>> +	struct pci_dev_resource *dev_res;
>> +
>> +	list_for_each_entry(dev_res, head, list) {
>> +		if (dev_res->res == res) {
>> +			int idx = res - &dev_res->dev->resource[0];
>> +
>> +			dev_printk(KERN_DEBUG, &dev_res->dev->dev,
>> +				   "res[%d]=%pR get_res_add_align min_align %llx\n",
>> +				   idx, dev_res->res,
>> +				   (unsigned long long)dev_res->min_align);
>> +
>> +			return dev_res->min_align;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +}
>
>I see that you copied the structure of the existing get_res_add_size()
>here.  But I don't understand *that* function.  It looks basically like
>this:
>
>  resource_size_t get_res_add_size(list, res)
>  {
>    list_for_each_entry(dev_res, head, list) {
>      if (dev_res->res == res)
>        return dev_res->add_size;
>    }
>    return 0;
>  }
>
>and we call it like this:
>
>  dev_res->res->end += get_res_add_size(realloc_head, dev_res->res);
>
>So we start out with dev_res", pass in dev_res->res, search the
>realloc_head list to find dev_res again, and return dev_res->add_size.
>That looks equivalent to just:
>
>  dev_res->res->end += dev_res->add_size;
>
>It looks like get_res_add_size() merely adds a printk and some complexity.
>Am I missing something?
>

Let me try to explain it, if not correct, please let know :-)

  dev_res->res->end += get_res_add_size(realloc_head, dev_res->res);

would be expanded to:

  dev_res->res->end += dev_res_1->add_size;

with the dev_res_1 is another one from dev_res which is stored in realloc_head.

>I do see that there are other callers where we don't actually start with
>dev_res, which makes it a little more complicated.  But I think you should
>either add something like this:
>
>  struct pci_dev_resource *res_to_dev_res(list, res)
>  {
>    list_for_each_entry(dev_res, head, list) {
>      if (dev_res->res == res)
>        return dev_res;
>    }
>    return NULL;
>  }
>

Ok, we can extract the common part of these two functions.

>which can be used to replace get_res_add_size() and get_res_add_align(), OR
>figure out whether the dev_res of interest is always one we've just added.
>If it is, maybe you can just make add_to_list() return the dev_res pointer
>instead of an errno, and hang onto the pointer.  I'd like that much better
>if that's possible.
>

Sorry, I don't get this point.

add_to_list() is used to create the pci_dev_resource list, get_res_add_size()
and get_res_add_align() is to retrieve the information in the list. I am not
sure how to leverage add_to_list() in these two functions?

>> +
>> +
>>  /* Sort resources by alignment */
>>  static void pdev_sort_resources(struct pci_dev *dev, struct list_head *head)
>>  {
>> @@ -368,8 +390,9 @@ static void __assign_resources_sorted(struct list_head *head,
>>  	LIST_HEAD(save_head);
>>  	LIST_HEAD(local_fail_head);
>>  	struct pci_dev_resource *save_res;
>> -	struct pci_dev_resource *dev_res, *tmp_res;
>> +	struct pci_dev_resource *dev_res, *tmp_res, *dev_res2;
>>  	unsigned long fail_type;
>> +	resource_size_t add_align, align;
>>  
>>  	/* Check if optional add_size is there */
>>  	if (!realloc_head || list_empty(realloc_head))
>> @@ -384,10 +407,31 @@ static void __assign_resources_sorted(struct list_head *head,
>>  	}
>>  
>>  	/* Update res in head list with add_size in realloc_head list */
>> -	list_for_each_entry(dev_res, head, list)
>> +	list_for_each_entry_safe(dev_res, tmp_res, head, list) {
>>  		dev_res->res->end += get_res_add_size(realloc_head,
>>  							dev_res->res);
>>  
>> +		if (!(dev_res->res->flags & IORESOURCE_STARTALIGN))
>> +			continue;
>> +
>> +		add_align = get_res_add_align(realloc_head, dev_res->res);
>> +
>> +		if (add_align > dev_res->res->start) {
>> +			dev_res->res->start = add_align;
>> +			dev_res->res->end = add_align +
>> +				            resource_size(dev_res->res);
>> +
>> +			list_for_each_entry(dev_res2, head, list) {
>> +				align = pci_resource_alignment(dev_res2->dev,
>> +							       dev_res2->res);
>> +				if (add_align > align)
>> +					list_move_tail(&dev_res->list,
>> +						       &dev_res2->list);
>> +			}
>> +               }
>> +
>> +	}
>> +
>>  	/* Try updated head list with add_size added */
>>  	assign_requested_resources_sorted(head, &local_fail_head);
>>  
>> @@ -930,6 +974,8 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>  	struct resource *b_res = find_free_bus_resource(bus,
>>  					mask | IORESOURCE_PREFETCH, type);
>>  	resource_size_t children_add_size = 0;
>> +	resource_size_t children_add_align = 0;
>> +	resource_size_t add_align = 0;
>>  
>>  	if (!b_res)
>>  		return -ENOSPC;
>> @@ -954,6 +1000,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>  			/* put SRIOV requested res to the optional list */
>>  			if (realloc_head && i >= PCI_IOV_RESOURCES &&
>>  					i <= PCI_IOV_RESOURCE_END) {
>> +				add_align = max(pci_resource_alignment(dev, r), add_align);
>>  				r->end = r->start - 1;
>>  				add_to_list(realloc_head, dev, r, r_size, 0/* don't care */);
>>  				children_add_size += r_size;
>> @@ -984,8 +1031,11 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>  			if (order > max_order)
>>  				max_order = order;
>>  
>> -			if (realloc_head)
>> +			if (realloc_head) {
>>  				children_add_size += get_res_add_size(realloc_head, r);
>> +				children_add_align = get_res_add_align(realloc_head, r);
>> +				add_align = max(add_align, children_add_align);
>> +			}
>>  		}
>>  	}
>>  
>> @@ -996,7 +1046,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>  		add_size = children_add_size;
>>  	size1 = (!realloc_head || (realloc_head && !add_size)) ? size0 :
>>  		calculate_memsize(size, min_size, add_size,
>> -				resource_size(b_res), min_align);
>> +				resource_size(b_res), max(min_align, add_align));
>>  	if (!size0 && !size1) {
>>  		if (b_res->start || b_res->end)
>>  			dev_info(&bus->self->dev, "disabling bridge window %pR to %pR (unused)\n",
>> @@ -1008,10 +1058,12 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>  	b_res->end = size0 + min_align - 1;
>>  	b_res->flags |= IORESOURCE_STARTALIGN;
>>  	if (size1 > size0 && realloc_head) {
>> -		add_to_list(realloc_head, bus->self, b_res, size1-size0, min_align);
>> -		dev_printk(KERN_DEBUG, &bus->self->dev, "bridge window %pR to %pR add_size %llx\n",
>> -			   b_res, &bus->busn_res,
>> -			   (unsigned long long)size1-size0);
>> +		add_to_list(realloc_head, bus->self, b_res, size1-size0,
>> +				max(min_align, add_align));
>> +		dev_printk(KERN_DEBUG, &bus->self->dev, "bridge window "
>> +				 "%pR to %pR add_size %llx add_align %llx\n", b_res,
>> +				 &bus->busn_res, (unsigned long long)size1-size0,
>> +				 max(min_align, add_align));
>
>Factor out this "max(min_align, add_align)" thing so we don't have to
>change these lines.  Bonus points if you can also factor it out of the
>calculate_memsize() call above.  That one is a pretty complicated ternary
>expression that should probably be turned into an "if" instead anyway.
>

Ok, I get your point. Let me make it more easy to read.

>>  	}
>>  	return 0;
>>  }
>> -- 
>> 1.7.9.5

-- 
Richard Yang
Help you, Help me